Camshaft adjusters are used in internal combustion engines to vary the control times of the combustion chamber valves to be able to vary the phase relation between the crankshaft and the camshaft in a defined angle range between a maximum advance position and a maximum retard position. Adjusting the control times to the instantaneous load and rotational speed reduces consumption and emissions. For this purpose, camshaft adjusters are integrated into a drive train, via which a torque is transferred from the crankshaft to the camshaft. This drive train may be designed, for example, as a belt, chain or gear drive.
In a hydraulic camshaft adjuster, the output element and the drive element form one or multiple pair(s) of counteracting pressure chambers to which a hydraulic medium is applied. The drive element and the output element are coaxially situated. A relative movement between the drive element and the output element is created by filling and emptying individual pressure chambers. The rotatively acting spring between the drive element and the output element pushes the drive element toward the output element in an advantageous direction. This advantageous direction may be in the same direction or in the opposite direction of the direction of rotation.
One design of the hydraulic camshaft adjuster is the vane adjuster. The vane adjuster includes a stator, a rotor and a drive wheel, which has an external toothing. The rotor as the output element is usually designed to be rotatably fixedly connectable to the camshaft. The drive element includes the stator and the drive wheel. The stator and the drive wheel are rotatably fixedly connected to each other or, alternatively, they are designed to form a single piece with each other. The rotor is situated coaxially with respect to the stator and inside the stator. Together with their radially extending vanes, the rotor and the stator form oppositely acting oil chambers, to which oil pressure may be applied and which facilitate a relative rotation between the stator and the rotor. The vanes are either designed to form a single piece with the rotor or the stator or are situated as “plugged-in vanes” in grooves of the rotor or stator provided for this purpose. The vane adjusters furthermore include various sealing covers. The stator and the sealing covers are secured to each other with the aid of multiple screw connections.
Another design of the hydraulic camshaft adjuster is the axial piston adjuster. In this case, a shifting element, which creates a relative rotation between a drive element and an output element via inclined toothings, is axially shifted with the aid of oil pressure.
A further design of a camshaft adjuster is the electromechanical camshaft adjuster, which has a three-shaft gear set (for example, a planetary gear set). One of the shafts forms the drive element and a second shaft forms the output element. Rotation energy may be supplied to the system or removed from the system via the third shaft with the aid of an actuating device, for example an electric motor or a brake. A spring may be additionally situated, which supports or feeds back the relative rotation between the drive element and the output element.
DE 10 2006 002 993 A1 shows a camshaft adjuster, which includes a chain wheel, a rotor, a housing and a spring. The housing and the rotor form the working chambers for the relative rotation. The chain wheel is rotatably fixedly connected to the housing. The spring is situated outside the housing and is protected against external contamination by an additional spring cover connected to the chain wheel, so that it is largely protected against external effects which shorten the service life. The rotor includes a pin which penetrates the housing and which provides a support for an elastic foot of the spring.